U.S. patent number 7,078,116 [Application Number 10/696,415] was granted by the patent office on 2006-07-18 for method of warming up fuel cell system.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Naoyuki Enjoji, Kazuya Sasamoto.
United States Patent |
7,078,116 |
Enjoji , et al. |
July 18, 2006 |
Method of warming up fuel cell system
Abstract
A fuel cell system includes a fuel cell, a heater provided in
the fuel cell, a load such as a peripheral component of the fuel
cell, a capacitor, and a switch. Power generation of the fuel cell
is carried out continuously for supplying electric energy to the
load, and charging the capacitor. When charging of the capacitor is
completed, the switch is operated such that electric energy
discharged from the capacitor is supplied to the heater for warming
up the fuel cell by the heater.
Inventors: |
Enjoji; Naoyuki (Utsunomiya,
JP), Sasamoto; Kazuya (Haga-gun, JP) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JP)
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Family
ID: |
32211780 |
Appl.
No.: |
10/696,415 |
Filed: |
October 28, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040091755 A1 |
May 13, 2004 |
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Foreign Application Priority Data
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Oct 31, 2002 [JP] |
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2002-318558 |
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Current U.S.
Class: |
429/429; 429/433;
429/452 |
Current CPC
Class: |
H01M
8/04701 (20130101); H01M 8/0267 (20130101); H01M
8/04007 (20130101); H01M 8/0488 (20130101); H01M
8/04225 (20160201); H01M 8/04731 (20130101); H01M
8/2465 (20130101); H01M 8/04223 (20130101); H01M
8/2457 (20160201); H01M 8/04302 (20160201); H01M
8/04373 (20130101); H01M 8/241 (20130101); H01M
8/04037 (20130101); Y02E 60/50 (20130101); H01M
16/003 (20130101) |
Current International
Class: |
H01M
8/00 (20060101) |
Field of
Search: |
;429/12,13 |
References Cited
[Referenced By]
U.S. Patent Documents
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5798186 |
August 1998 |
Fletcher et al. |
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Foreign Patent Documents
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2003-308863 |
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Oct 2003 |
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JP |
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2004-281219 |
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Oct 2004 |
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JP |
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2004-288530 |
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Oct 2004 |
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JP |
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2005-050638 |
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Feb 2005 |
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JP |
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Primary Examiner: Ryan; Patrick Joseph
Assistant Examiner: Parsons; Thomas H.
Attorney, Agent or Firm: Lahive & Cockfield, LLP
Laurentano, Esq.; Anthony A.
Claims
What is claimed is:
1. A method of warming up a fuel cell system including a fuel cell,
a heater for heating said fuel cell, and a capacitor electrically
connected to said fuel cell, said fuel cell comprising an
electrolyte electrode assembly including a pair of electrodes and
an electrolyte interposed between said electrodes, and separators
for sandwiching said electrolyte electrode assembly, said method
comprising the steps of: generating electric energy continuously in
said fuel cell for supplying electric energy to a peripheral
component of said fuel cell; supplying electric energy to said
capacitor for charging said capacitor; and supplying electric
energy discharged from said capacitor to said heater for warming up
said fuel cell by said heater, wherein charging and discharging of
said capacitor are repeated during the continuous operation of said
fuel cell.
2. A warming up method according to claim 1, wherein said capacitor
includes first and second capacitors arranged in parallel with each
other, and selectively connectable to said fuel cell; said method
comprising the steps of: connecting said fuel cell and said first
capacitor for charging said first capacitor while supplying
electric energy discharged from said second capacitor to said
heater; and connecting said fuel cell and said second capacitor for
charging said second capacitor while supplying electric energy
discharged from said first capacitor to said heater.
3. A warming up method according to claim 2, wherein said first and
second capacitors are connectable to said fuel cell through a
transformer; and a voltage generated by said fuel cell is reduced
by half by said transformer, and applied alternately to said first
and second capacitors for charging said first and second
capacitors.
4. A warming up method according to claim 2, wherein after warming
up operation is finished, said first and second capacitors are
electrically connected in series with each other.
5. A warming up method according to claim 2, wherein said fuel cell
includes first and second fuel cells arranged in parallel with each
other, and said heater includes a first heater for heating said
first fuel cell and a second heater for heating said second fuel
cell, said method comprising the steps of: connecting said first
and second fuel cells and said first capacitor for charging said
first capacitor while supplying electric energy discharged from
said second capacitor to said second heater for warming up said
second fuel cell; and connecting said first and second fuel cells
and said second capacitor for charging said second capacitor while
supplying electric energy discharged from said first capacitor to
said first heater for warming up said first fuel cell.
6. A warming up method according to claim 5, wherein after warming
up operation is finished, said first and second fuel cells are
electrically connected in series with each other, and said first
and second capacitors are electrically connected in series with
each other.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of warming up a fuel cell
system including a fuel cell, a heater for heating the fuel cell,
and a capacitor electrically connected to the fuel cell. The fuel
cell includes an electrolyte electrode assembly interposed between
a pair of separators. The electrolyte electrode assembly includes a
pair of electrodes, and an electrolyte interposed between the
electrodes.
2. Description of the Related Art
Generally, a solid polymer electrolyte fuel cell employs a membrane
electrode assembly (MEA) which comprises two electrodes (anode and
cathode) and an electrolyte membrane interposed between the
electrodes. The electrolyte membrane is a polymer ion exchange
membrane. The membrane electrode assembly is interposed between
separators. The membrane electrode assembly and the separators make
up a unit of the fuel cell for generating electricity. A
predetermined number of fuel cells are stacked together to form a
fuel cell stack.
In the fuel cell, a fuel gas such as a hydrogen-containing gas is
supplied to the anode. The catalyst of the anode induces a chemical
reaction of the fuel gas to split the hydrogen molecule into
hydrogen ions (protons) and electrons. The hydrogen ions move
toward the cathode through the electrolyte, and the electrons flow
through an external circuit to the cathode, creating a DC electric
current. An oxygen-containing gas or air is supplied to the
cathode. At the cathode, the hydrogen ions from the anode combine
with the electrons and oxygen to produce water.
If the fuel cell has a low temperature at the time of starting
operation, power generation can not be performed efficiently. It
takes considerable time to raise the temperature of the fuel cell
to a desired temperature for power generation. In particular, if
operation of the fuel cell is started at a temperature below zero
(freezing temperature), water condensation is likely to occur due
to the heat radiated outwardly from the fuel cell, and the water
produced in the reaction of the fuel cell is not smoothly
discharged from the fuel cell. Thus, the desired power generation
performance of the fuel cell may not be achieved.
In an attempt to address the problem, the U.S. Pat. No. 5,798,186
discloses a fuel cell system in which a fuel cell stack is
connected to an external electrical circuit, and the supply of
electric current to the external electrical circuit from the fuel
cell stack is commenced such that the temperature of the membrane
electrode assembly exceeds the freezing temperature of water.
In the fuel cell system of the U.S. patent, the temperature of the
entire fuel cell stack is raised by self-heating. If operation of
the fuel cell stack is started at a low temperature, a large amount
of heat energy is needed for warming up the entire fuel cell stack.
If an electrical heater is used for warming up the fuel cell stack,
a considerably long time is needed, and the electrical heater needs
to have a considerably large electric capacity. In particular, if
operation of the fuel cell stack is started at a temperature below
the freezing temperature, the water produced in the fuel cell stack
may be frozen undesirably in the gas diffusion layers or reactant
gas passages, and the warming up operation may not be carried out
continuously.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide a method of
warming up a fuel cell system in which the fuel cell system is
warmed up reliably in a short period of time by a simple process,
and operation of the fuel cell system can be started rapidly.
According to the present invention, electric energy is generated
continuously in a fuel cell for supplying electric energy to a
peripheral component of the fuel cell. Electric energy is supplied
to a capacitor (energy storing device) for charging the capacitor.
Electric energy discharged from the capacitor is supplied to a
heater for warming up the fuel cell by the heater. Charging and
discharging of the capacitor are repeated during the continuous
operation of the fuel cell.
Thus, the fuel cell is self-heated in generating electric energy
for the load of the peripheral component and the load for charging
the capacitor. The fuel cell is warmed up rapidly by the continuous
power generation. The capacitor is also warmed up rapidly while
charging and discharging of the capacitor are carried out
repeatedly. With the simple process, the fuel cell and the
capacitor are warmed up reliably in a short period of time, and
operation of the fuel cell system can be started efficiently at a
low temperature. The fuel cell and the capacitor can function
desirably even if operation of the fuel cell system is started at a
low temperature. The reliable warming up operation ensures the
desired functions of the components in the fuel cell system, and
operation of the fuel cell system can be started desirably at a low
temperature.
In one embodiment, first and second capacitors are arranged in
parallel with each other, and selectively connectable to the fuel
cell. When the fuel cell is connected to the first capacitor for
charging the first capacitor, electric energy is discharged from
the second capacitor, and supplied to the heater. When the fuel
cell is connected to the second capacitor for charging the second
capacitor, electric energy is discharged from the first capacitor,
and supplied to the heater.
Electric energy is supplied alternately from the first and second
capacitors to the heater for warming up the fuel cell. The heater
is continuously operated for heating the fuel cell, and thus, the
fuel cell is warmed up reliably in a short period of time.
In one embodiment, first and second fuel cells are arranged in
parallel with each other. Warming up operation is controlled
simply. After warming up operation is finished, the first and
second fuel cells are electrically connected in series with each
other, and the first and second capacitors are electrically
connected in series with each other.
The above and other objects, features and advantages of the present
invention will become more apparent from the following description
when taken in conjunction with the accompanying drawings in which
preferred embodiments of the present invention are shown by way of
illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view schematically showing a fuel cell system according
to a first embodiment of the present invention;
FIG. 2 is a timing chart showing operation of a fuel cell and a
capacitor in the fuel cell system;
FIG. 3 is a view showing operation in which electric energy is
discharged from the capacitor in the fuel cell system;
FIG. 4 is a view schematically showing a fuel cell system according
to a second embodiment of the present invention;
FIG. 5 is a timing chart showing operation of a fuel cell and first
and second capacitors;
FIG. 6 is a view showing operation in which electric energy is
discharged from the first capacitor, and electric energy is charged
in the second separator;
FIG. 7 is a view showing normal operation of the fuel cell
system;
FIG. 8 is a view showing a fuel cell system according to a third
embodiment of the present invention;
FIG. 9 is a view showing a fuel cell system according to a fourth
embodiment of the present invention; and
FIG. 10 is a view showing normal operation of the fuel cell
system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a view schematically showing a fuel cell system 10
according to a first embodiment of the present invention.
The fuel cell system 10 includes at least one fuel cell 12, a
heater 14 provided in the fuel cell 12 for heating the fuel cell
12, a capacitor (energy storing device) 16 electrically connected
to the fuel cell 12, and a switch 20 for selectively connecting the
capacitor 16 to the fuel cell 12 and the heater 14. In the
embodiment, the fuel cell 12 is directly heated by the heater 14.
Though not shown, a heater for heating a coolant may be used
alternatively.
In FIG. 1, a plurality of fuel cells 12 are stacked together in a
direction indicated by an arrow A to form a fuel cell stack.
Alternatively, the fuel cell system 10 includes only a single fuel
cell 12. The fuel cell 12 includes a membrane electrode assembly 22
and first and second separators 24, 26 for sandwiching the membrane
electrode assembly 22. The membrane electrode assembly 22 comprises
an anode 32, a cathode 34, and a solid polymer electrolyte membrane
30 interposed between the anode 32 and the cathode 34. The solid
polymer electrolyte membrane 30 is formed by impregnating a thin
membrane of perfluorosulfonic acid with water, for example.
Each of the anode 32 and the cathode 34 has a gas diffusion layer
such as a porous carbon paper, and an electrode catalyst layer of
platinum alloy supported on porous carbon particles. The carbon
particles of the electrode catalyst layer are deposited uniformly
on the surface of the gas diffusion layer. The electrode catalyst
layer of the anode 32 and the electrode catalyst layer of the
cathode 34 are fixed to both surfaces of the solid polymer
electrolyte membrane 30, respectively.
The first separator 24 has a fuel gas flow field 35 on its surface
facing the membrane electrode assembly 22 for supplying a fuel gas
such as a hydrogen-containing gas to the anode 32. The second
separator 26 has an oxygen-containing gas flow field 36 on its
surface facing the membrane electrode assembly 22 for supplying an
oxygen-containing gas to the cathode 34. A coolant flow field 38
for supplying a coolant to cool the membrane electrode assembly 22
is formed between the first and second separators 24, 26.
The fuel cell 12 and a load 18 is connected in parallel with each
other. One end of the fuel cell 12, and one end of the heater 14 is
connected to one end of the capacitor 16. The other end of the fuel
cell 12 is connected to a first contact 40 of a switch 20, and the
other end of the heater 14 is connected to a second contact 42 of
the switch 20. The other end of the capacitor 16 is connected to a
common contact 44 of the switch 20. The common contact 44 is
selectively connected to the first contact 40 and the second
contact 42 for selectively connecting the capacitor 16 to the fuel
cell 12 and the heater 14.
Operation of the fuel cell system 10 will be described below with
reference to a timing chart shown in FIG. 2.
If operation of the fuel cell system 10 is started at a temperature
below the freezing point, for example, the condensed water may be
frozen undesirably during the operation. Thus, it is necessary to
warm up the fuel cell system 10. In FIG. 1, the common contact 44
of the switch 20 is connected to the first contact 40. The
capacitor 16 and the load 18 are electrically connected to the fuel
cell 12. Under the condition, power generation of the fuel cell 12
is performed.
Specifically, a fuel gas such as a hydrogen-containing gas is
supplied to the fuel gas flow field 35 on the first separator 24
for inducing an electrochemical reaction at the anode 32, and an
oxygen-containing gas is supplied to the oxygen-containing gas flow
field 36 on the second separator 26 for inducing an electrochemical
reaction at the cathode 34. In the membrane electrode assembly 22,
the fuel gas supplied to the anode 32, and the oxygen-containing
gas supplied to the cathode 34 are consumed in the electrochemical
reactions at the electrode catalyst layers of the anode 32 and the
cathode 34 for generating electricity.
Further, a coolant heated by a heater (not shown) as necessary is
supplied to the coolant flow field 38 between the first and second
separators 24, 26. At the time of starting operation of the fuel
cell 12, the temperature of the coolant is low. The supply of the
coolant to the coolant flow field 38 may be stopped at the time of
starting operation of the fuel cell 12 for preventing the fuel cell
12 from being cooled by the coolant undesirably.
As described above, when the capacitor 16 is connected electrically
to the fuel cell 12 during power generation of the fuel cell 12,
electric energy supplied from the fuel cell 12 is charged in the
capacitor 16. Further, the fuel cell 12 supplies electric energy to
the load 18 for driving periphery components of the fuel cell 12
such as a pump for supplying the fuel gas and a pump for supplying
the oxygen-containing gas.
When electric charging of the capacitor 16 is completed, the switch
20 is operated to connect the common contact 44 to the second
contact 42. Therefore, the capacitor 16 is disconnected from the
fuel cell 12, and connected to the heater 14. Electric energy is
discharged from the capacitor 16, and supplied to the heater 14.
Thus, the heater 14 in the fuel cell 12 warms up the fuel cell
12.
When electric discharging of the capacitor 16 is completed, the
switch 20 is operated to connect the common contact 44 to the first
contact 40. Therefore, the capacitor 16 is disconnected from the
heater 14, and connected to the fuel cell 12.
As describe above, switching operation of the switch 20 is carried
out for repeating electric charging and discharging of the
capacitor 16 alternately. The temperature of the heater 14 is
raised to warm up the fuel cell 12. During the electric discharge
period of the capacitor 16, power generation of the fuel cell 12 is
performed continuously for supplying electric energy to the load
18.
In the first embodiment, the fuel cell 12 is self-heated in
generating electric energy for the load 18 of the peripheral
component and the load for charging the capacitor 16. The fuel cell
12 is warmed up rapidly by the continuous power generation. The
capacitor 16 is also self-heated while charging and discharging of
the capacitor are carried out repeatedly, and thus, the capacitor
16 is warmed up rapidly. With the simple process, the fuel cell 12
and the capacitor 16 are warmed up reliably in a short period of
time, and operation of the fuel cell system 10 can be started
rapidly at a low temperature.
If the fuel cell 12 and the capacitor 16 are operated for moving
the vehicle, for example, before the fuel cell 12 and the capacitor
16 are warmed up sufficiently, the fuel cell 12 and the capacitor
16 do not function properly. As described above, the fuel cell 12
and the capacitor 16 according to the present embodiment can be
warmed up reliably in a short period of time. Thus, the fuel cell
system 10 using the fuel cell 12 and the capacitor 16 is capable of
moving the vehicle with a high performance.
After warming up operation is completed, the switch 20 is operated
to connect the common contact 44 to the first contact 40, and the
fuel cell 12 is connected to the capacitor 16 (see FIG. 1).
Under the condition, the capacitor 16 is suitably utilized,
typically, as an acceleration assisting component or a regenerative
braking component.
FIG. 4 is a view schematically showing a fuel cell system 60
according to a second embodiment of the present invention. In FIG.
4, the constituent elements that are identical to those of the fuel
cell system 10 according to the first embodiment are labeled with
the same reference numeral, and description thereof is omitted.
The fuel cell system 60 includes first and second capacitors 16a,
16b arranged in parallel with each other, a transformer 62, and
first through fifth switches 20a, 20b, 20c, 20d, 20e. When electric
energy is charged in the first and second capacitors 16a, 16b
alternately, the transformer 62 reduces the voltage applied to the
first capacitor 16a or the second capacitor 16b by half.
The first switch 20a has a first contact 40a connected to the
heater 14, a second contact 42a connected to the lower voltage side
of the transformer 62, and a common contact 44a connected to the
first capacitor 16a. The second switch 20b has a first contact 40b
connected to the heater 14, a second contact 42b connected to the
fuel cell 12, a third contact 64 connected to the lower voltage
side of the transformer 62, and a common contact 44b connected to
the second capacitor 16b.
The third switch 20c has a first contact 40c connected to the first
capacitor 16a, and a second contact 42c connected to the lower
voltage side of the transformer 62, and a common contact 44c
connected to the second capacitor 16b. The fourth switch 20d has a
first contact 40d connected to the fifth switch 20e, a second
contact 42d connected to the lower voltage side of the transformer
62, and a common contact 44d connected to the first capacitor
16a.
The fifth switch 20e has a first contact 40e connected to the
higher voltage side of the transformer 62, and a second contact 42e
connected to the fourth switch 20d, and a common contact 44e
connected to the fuel cell 12.
In the second embodiment, at the time of starting the operation of
the fuel cell system 60 at a low temperature, the fuel cell 12, the
first and second capacitors 16a, 16b are warmed up in a manner as
shown in a timing chart shown in FIG. 5.
In FIG. 4, the common contact 44a of the first switch 20a is
connected to the second contact 42a, the common contact 44b of the
second switch 20b is connected to the first contact 40b, the common
contact 44c of the third switch 20c is connected to the second
contact 42c, the common contact 44d of the fourth switch 20d is
connected to the second contact 42d, and the common contact 44e of
the fifth switch 20e is connected to the first contact 40e.
When the power generation is performed in the fuel cell 12 for
supplying electric energy to the load 18, the transformer 62
reduces the voltage of the fuel cell 12 by half, and applies the
reduced voltage to the first capacitor 16a for charging the first
capacitor 16a. The second capacitor 16b is electrically connected
to the heater 14. Electric energy is discharged from the second
capacitor 16b, and supplied to the heater 14. Thus, the fuel cell
12 is warmed up by the heater 14.
Then, when charging of the first capacitor 16a and discharging of
the second capacitor 16b are completed, electrical connections are
changed by the first and second switches 20a, 20b as shown in FIG.
6. The first capacitor 16a is electrically connected to the heater
14 through the first and fourth switches 20a, 20d. Electric energy
discharged from the first capacitor 16a is supplied to the heater
14, and the fuel cell 12 is warmed up continuously. The second
capacitor 16b is connected to the lower voltage side of the
transformer 62 through the second and third switches 20b, 20c.
Electric energy from the fuel cell 12 is supplied to the second
capacitor 16b for charging the second capacitor 16b.
When discharging of the first capacitor 16a and charging of the
second capacitor 16b are completed, electrical connections are
changed by the first and second switches 20a, 20b as shown in FIG.
4. Charging of the first capacitor 16a and discharging of the
second capacitor 16b are started again, and the first and second
capacitors 16a, 16b are warmed up.
After the fuel cell 12 and the first and second capacitor 16a, 16b
are warmed up as described above, electric connections are changed
by the first through fifth switches 20a through 20e as shown in
FIG. 7. The fuel cell 12, and the first and second capacitors 16a,
16b are connected in series to enter the normal operation mode.
In the second embodiment, the first and second capacitors 16a, 16b
are arranged in parallel with each other, and selectively connected
to the fuel cell 12 during the warming up operation. When the first
capacitor 16a is connected to the fuel cell 12 for charging the
first capacitor 16a by the fuel cell 12, the second capacitor 16b
is connected to the heater 14, and electric energy discharged from
the second capacitor 16b is supplied to the heater 14. Then, when
the second capacitor 16b is connected to the fuel cell 12 for
charging the second capacitor 16b by the fuel cell 12, the first
capacitor 16a is connected to the heater 14, and electric energy
discharged from the first capacitor 16a is supplied to the heater
14.
The first and second capacitors 16a, 16b are alternately discharged
for supplying electric energy to the heater 14. Thus, electric
energy is continuously supplied to the heater 14 for heating the
fuel cell 12. Since the fuel cell 12 is self-heated by its power
generating operation, and continuously heated by the heater 14, the
fuel cell 12 is efficiently warmed up in a short period of
time.
FIG. 8 is a view schematically showing a fuel cell system 80
according to a third embodiment of the present invention. In FIG.
8, the constituent elements that are identical to those of the fuel
cell system 60 according to the first embodiment are labeled with
the same reference numeral, and description thereof is omitted.
The fuel cell system 80 includes first and second capacitors 16c,
16d. The voltage applied to the first and second capacitors 16c,
16d is same as the voltage generated by the fuel cell 12. The first
and second capacitors 16c, 16d are arranged in parallel with each
other, and selectively connected to the fuel cell 12 through the
first through fourth switches 20a through 20d. In the third
embodiment, the transformer 62 and the fifth 20e of the fuel cell
system 60 according to the second embodiment are not employed.
In the fuel cell system 80, the first through fourth switches 20a
through 20d are operated as shown by solid lines in FIG. 8 in
supplying electric energy of the fuel cell 12 to the first
capacitor 16c for charging the first capacitor 16c, and supplying
the energy discharged from the second capacitor 16d to the heater
14. Then, the first through fourth switches 20a through 20d are
operated as shown by two-dot chain lines in FIG. 8 in supplying
electric energy of the fuel cell 12 to the second capacitor 16d for
charging the second capacitor 16d, and supplying electric energy
discharged from the first capacitor 16c to the heater 14.
In the third embodiment, the fuel cell system 80 has a simple
structure, and controlled simply. Electric energy is continuously
supplied from the first and second capacitors 16c, 16d to the
heater 14. Thus, the fuel cell 12 can be warmed up efficiently in a
short period of time, as with the first and second embodiments.
FIG. 9 is a view schematically showing a fuel cell system 90
according to a fourth embodiment of the present invention. In FIG.
9, the constituent elements that are identical to those of the fuel
cell system 80 according to the third embodiment are labeled with
the same reference numeral, and description thereof is omitted.
The fuel cell system 90 includes first and second fuel cells 12a,
12b. The first and second fuel cells 12a, 12b are connected in
parallel with each other during warming up operation. A first
heater 14a is provided in the first fuel cell 12a, and a second
heater 14b is provided in the second fuel cell 12b. Fifth and sixth
switches 20e, 20f are used for selectively connecting the first and
second fuel cells 12a, 12b in parallel or in series.
The fifth switch 20e has a common contact 44e connected to the
first fuel cell 12a, a first contact 40e connected to the first
switch 20a, and a second contact 42e connected to the sixth switch
20f. The sixth switch 20f has a first contact 40f connected to the
fifth switch 20e, a second contact 42f connected to the third and
fourth switches 20c, 20d, and a common contact 44f connected to the
second fuel cell 12b. The third switch 20c has a third contact 64c
connected to the second heater 14b, in addition to the first and
second contacts 40c, 42c.
In the fourth embodiment, when operation of the fuel cell system 90
is started at a low temperature, the first through sixth switches
20a through 20f are operated as shown by solid lines in FIG. 9.
Electric energy generated by the first and second fuel cells 12a,
12b is supplied to the load 18. Further, electric energy is
supplied to the first capacitor 16a for charging the first
capacitor 16a. The second capacitor 16b is connected to the second
heater 14b, and electric energy discharged form the second
capacitor 16b is supplied to the second heater 14b for warming up
the second fuel cell 12b.
When charging of the first capacitor 16a and discharging of the
second capacitor 16b are completed, the first through fourth
switches 20a through 20d are operated as shown by two dot lines in
FIG. 9 for changing electrical connections. Electric energy
generated by the first and second fuel cells 12a, 12b is supplied
to the second capacitor 16b for charging the second capacitor 16b.
The first capacitor 16a is connected to the first heater 14a, and
electric energy discharged form the first capacitor 16a is supplied
to the first heater 14a for warming up the first fuel cell 12a.
The first and second capacitors 16a, 16b are charged and discharged
alternately and repeatedly by the switching operation of the first
through fourth switches 20a through 20d. The first and second fuel
cells 12a, 12b are self-heated during the power generation, and
also heated by the heaters 14a, 14b, respectively. The first and
second capacitors 16a, 16b are self-heated while the first and
second capacitors 16a, 16b are charged and discharged
repeatedly.
The fuel cell system 90 has a simple structure, and operation of
the fuel cell system 90 is controlled simply. The first and second
fuel cells 12a, 12b, and the first and second capacitors 12a, 12b
are warmed up efficiently in a short period of time, as with the
first through third embodiments.
In the fourth embodiment, the first through sixth switches 20a
through 20f are operated as shown in FIG. 10 during the normal
operation. The first and second fuel cells 12a, 12b are connected
in series with each other for generating a desired voltage, and the
first and second capacitors 16a, 16b are connected in series with
each other for use as, typically, acceleration assisting components
or regenerative braking components.
In the method of warming up a fuel cell system according to the
present invention, electric energy is generated continuously in a
fuel cell for supplying electric energy to a peripheral component
of the fuel cell. Electric energy is supplied to a capacitor for
charging the capacitor. Electric energy discharged from the
capacitor is supplied to a heater for warming up the fuel cell by
the heater. Charging and discharging of the capacitor are repeated
during the continuous operation of the fuel cell.
Thus, the fuel cell is self-heated in generating electric energy
for the load of the peripheral component and the load for charging
the capacitor. The fuel cell is warmed up rapidly by the continuous
power generation. The capacitor is also warmed up rapidly while
charging and discharging of the capacitor are carried out
repeatedly. With the simple process, the fuel cell and the
capacitor are warmed up reliably in a short period of time, and
operation of the fuel cell system can be started efficiently at a
low temperature.
While the invention has been particularly shown and described with
reference to preferred embodiments, it will be understood that
variations and modifications can be effected thereto by those
skilled in the art without departing from the spirit and scope of
the invention as defined by the appended claims.
* * * * *